Pre-treatment methods for straw for farm-scale biogas plants

Abstract

This study investigated the effect of five different pre-treatment methods (ammonia (NH3), caustic soda (NaOH), dry milling, hot water and steam explosion) for straw for biogas production. The methods were selected based on their suitability for implementation in farm-scale biogas plants. The pre-treatment methods were applied to four different types of straw. Batch anaerobic digestion tests were carried out in bottles at mesophilic temperature (37 ± 1 °C). The straw was analysed for lignin, hemicellulose and cellulose. The results showed large variations in methane production following the different pre-treatment methods. There were also large variations between the pre-treatment methods in their effect on the different types of straw. Pre-treatment with NaOH on barley straw was particularly effective. The results also showed that the shorter the retention time in the reactor, the more important the choice of pre-treatment method. Different pre-treatment methods were found to be optimal, to some extent, for different retention times.